A Couple’s Journey through Fifty Year’s
of Ionospheric Space Weather Research
Sunanda Basu and Santimay Basu*
Boston College
CEDAR Workshop
Boulder, CO
23-28 June 2013
*Deceased 16 April 2013
Santimay Basu’s Obituary appeared in
SPA Newsletter dated May 1, 2013
Scope of Presentation
• Sunanda’s Grad Student Years
– Master’s in US – awesome discovery! Boston Globe
Photo June 1963
– Ph.D. in India (a son born in between)
• Santi’s Beacon Receiver Building Phase
– In India with his grad students
•
•
•
•
Sunanda’s Exciting NRC Post-doc Research
Sunanda and Santi Partnership Phase 1
Sunanda’s NSF Decade – AER/CEDAR
Sunanda and Santi Partnership Phase 2
Study of High Latitude Scintillations by
Receiving Signals from Artificial Satellites
One of the first
studies of high
latitude scintillations
using satellites was
made at Boston, MA
in the early sixties by
Jules Aarons and his
group. The Soviet
satellite Cosmos 1
and American
satellite Transit 4A
were used.
Dependence of
irregularities on
signal frequency,
latitude and magnetic
activity were
determined.
Sagamore Hill, MA
Sunanda Basu, MS Thesis, Boston Univ., 1963
Advisor: Gerald Hawkins
Su. Basu et al., JATP, 1964; Aarons, Mullen and
Basu, JGR, 1963;1964.
Vertical profile of
the ionosphere
Incident Plane Wave
TEC = 30 x 1016 m -2
Irregular Layer
Emerging Wavefront
Observer’s Plane
Pictorial illustration of the phase fluctuations
imposed on a wave-front traveling away from an
irregular layer for a vertical radio path.
For Scintillation Theory, see CEDAR Tutorial 2003
by Santimay Basu
What are the major impacts of scintillation?
Advantage of scintillation
technique is in simplicity
of the receiving system
that can be used when
the source is a satellite
(high signal strength).
Thus suitable also for
developing countries
(awesome discovery!)
• Regional UHF Communication outages for extended periods (hours)
• Increased Global Positioning Satellite (GPS) navigation errors
• Degraded High Frequency (HF) radio communication
Obstacles on the path to Sunanda’s Ph.D.
• Expectation was that I would teach under-graduate
Physics at a college for women – no opportunity to
combine with research
• Research in Radio Physics only possible at Calcutta
University where Santi was on the faculty
• Head of the Dept. there said he wouldn’t admit a woman
• I was equally adamant that I would do research ( we
decided to have a baby while waiting for an opening!!)
• Six months after the birth of our son, we found another
University in Calcutta called Jadavpur where the Head of
Telecommunication Engg. was more open minded
• I started work there with a junior fellowship from the
UGC in June 1965 – a group of one with the expectation
that Santi would provide guidance – and I haven’t
stopped doing research since!
Satellite signals received at Jadavpur & Haringhata
20 Mc/s
BEC
Su. Basu, JGR, 1967
40 Mc/s
Basu & Das Gupta, JGR, 1967
Latitude
Variation of TEC
Basu & Das Gupta, JGR, 1967
Magneto-ionic Mode
Coupling
Su. Basu & S. Basu, JGR, 1969
Summary of Scientific Studies in Space Weather
at Calcutta during 1965-1975
•Calcutta is located under the
Northern Crest of the Equatorial
Anomaly
•Total Electron Content variation with
satellites BE-B and BE-C measured
at Haringhata could map the
equatorial anomaly and its variations
with magnetic activity
•Magneto-ionic mode coupling and
studies on refraction correction in
the low latitude ionosphere were also
performed at Jadavpur University
( Some Publications: Su. Basu, JGR,
1967; S. Basu and DasGupta, JGR, 1967,
1968, 1969; Su. Basu and S. Basu, JGR,
1969, 1971, 1972; DasGupta and S. Basu,
Ann. Geophys, 1973)
Dr. Jules Aarons with Prof. M. K.
DasGupta, S. Basu and former
students, A. DasGupta, S. Mitra
and B.K. Guhathakurta at the
Field Station in February, 1969.
Susanto Basu, our son the
future economics prof at age
4, not too thrilled to be in the
company of grazing sheep in
the Calcutta Maidan!
Photo taken by Jules Aarons
during his 1969 Calcutta visit
Third International Symposium on Equatorial
Aeronomy, Ahmedabad, India, 1969
Chapman
1888-1970
Su.
Basu
Sarabhai
19191971
Scope of Presentation
Sunanda’s Grad Student Years
– Master’s in US – awesome discovery!
– Ph.D. in India (a son born in between)
Santi’s Beacon Receiver Building Phase
– In India with his grad students
•
•
•
•
Sunanda’s Exciting NRC Post-doc Research
Sunanda and Santi Partnership Phase 1
Sunanda’s NSF Decade – AER/CEDAR
Sunanda and Santi Partnership Phase 2
Model of Equatorial Scintillation
From Satellite In-Situ Measurements
• The OGO-6 Retarding Potential
Analyzer (RPA) data were made
available to us in Calcutta by Prof.
W.B. Hanson in 1974 (30 lb. data)
• The in-situ measurements of Fregion irregularity amplitude and
ambient electron density made by the
RPA on OGO-6 near the perigee
altitude of 400 km was utilized to
determine the electron density
deviation over the equatorial region.
• A model of equatorial scintillation
was developed in the framework of
diffraction theory and 3-D irregularity
power law index 4.
• The occurrence contours of 140
MHz scintillations during 19 – 23 MLT
for Nov-Dec period were derived.
A pronounced longitude variation of
the scintillation belt width and the
occurrence was obtained in
agreement with observations.
(Su. Basu et al., Radio Sci., 1976)
This was our first exposure to in-situ data and
was followed by work with AE-D, AE-E and DE-2
all made available to us by Bill Hanson.
Scintillatiions are most sensitive to
density irregularities of sizes of Fresnel
dimension L f ~ 1 km at VHF. Here outer
scale Lo ~ 20 km, distance traveled by
satellite in 3 sec, over which dN/N computed
by OGO-6. Thus spectral shape has to be
assumed to compute PSD at L f . A 3-D
power law irregularity power spectrum with
spectral index p = 4 used to compute
scintillation (Rufenach, Radio Sci., 1975).
Scope of Presentation
Sunanda’s Grad Student Years
– Master’s in US – awesome discovery!
– Ph.D. in India (a son in between)
Santi’s Beacon Receiver Building Phase
– In India with his grad students
Sunanda’s Exciting NRC Post-doc Research
• Sunanda and Santi Partnership Phase 1
• Sunanda’s NSF Decade – AER/CEDAR
• Sunanda and Santi Partnership Phase 2
Coordinated Jicamarca Radar and Scintillation Measurements
at the Magnetic Equator
In 1977, we performed for the first
time co-ordinated 50 MHz radar and
137 MHz scintillation through a
common ionospheric volume at the
magnetic equator. It established that at
the onset of spread-F, 3-m (50 MHz
radar) and km-scale (137 MHz
scintillation) irregularities attain
saturation amplitude simultaneously.
Later in the evening meter scale
irregularities decay faster than kmscales owing to scale-length
dependent cross-field diffusion
coefficients.
This confirmed Gerhard Haerendel’s
theory of equatorial spread F
(unpublished manuscript, 1974) that
mother and daughter irregularities
attain maturity at the same time
because the growth rate of smaller
irregularities is faster.
(Basu et al., JGR, 1978)
Observing Sites in the Equatorial Region used by AFRL to Determine
Ionospheric Constraints on Communication and Navigation Systems
Ascension Island in the South
Atlantic has one of the most
strongly turbulent
ionospheres. Since the midseventies AFRL has used this
ground station as the test bed
for studying the robustness of
communication and navigation
systems. The multi-frequency
scintillation input allowed the
development of user-oriented
scintillation models
A First Day cover showing the tiny size of Asc. Is.
Jicamarca radar, in Peru, at the
magnetic equator allows us to
study the initiation of
equatorial plasma turbulence.
Campaigns were conducted
starting in the mid-seventies to
understand F-region dynamics
The fully steerable Altair radar
has been used by AFRL
starting in the eighties to study
the physics of ionospheric
turbulence and assess their
impact on space surveillance.
ALTAIR Radar 46m
dish at VHF/UHF
Jicamarca Radar at 49.9 MHz
uses 18,432 dipoles
Quiet-time Space Weather:
Intense Scintillation Event at Ascension Island
The AFSATCOM system
provides Critical Satellite
Communications
support to the civilian
community and military .
“We are learning that space
weather can have a
significant effect on our
communications…..We must
provide either reliable
communications or at least a
forecast of when there will
be disruptions……”
Under solar maximum conditions,
20 decibel signal fadings at 1.5 GHz
(GPS frequency band) and
6 decibel fadings at 4 GHz are routinely
encountered at places like Ascension Island.
Voice communication becomes choppy, and
GPS position errors become unacceptable.
Chief,
AFSATCOM Systems Division
(Basu et al., IEEE, SAC-5, 1987)
Polar Cap VHF Scintillation Variation with
Solar Cycle
(Basu et al., Radio Sci., 1988)
Polar Cap Patches
PATCH STRUCTURING
Model plasma transport
By induced IMF variation
UT and seasonal effects
- Model reproduces
observed effects
Gradient drift structuring
causes observed
scintillation
DAYSIDE PLASMA
POLAR
CAP
MODEL NmF2
(Basu et al., GRL, 1995)
OBSERVED UHF SCINTILLATION
OBSERVED NmF2
Experiments in the Dark Cusp
Ny Alesund, at the dayside
cusp, is the entry point of
polar cap patches and the
seat of intense
scintillation. We went on a
2-week campaign,
obtained good data and
left the instruments there.
AFRL continues to
perform round-the-clock
scintillation and optical
observations throughout
the polar region in winter
(Basu, et al., Radio Sci.,
1994)
It is also Polar Bear
country, particularly In
winter, when we make our
observations. We were
asked to carry a gun when
going off the base!
Global Satcom Outage Regions
POLAR CAP
PATCHES
AURORAL IRREGULARITIES
SATCOM
GPS
PLASMA DEPLETIONS
EQUATORIAL F LAYER
ANOMALIES
GEOSAT
WEATHER
MAGNETIC Day
EQUATOR
Night
GEOSATCOM
Global Morphology of Scintillations
(Basu et al., Radio Sci., 1988)
Controlled Excitation of Plasma Processes in the Middle Latitude
Ionosphere by High Power HF Radio Waves
In March 1980, we used the Platteville High
Power (1.5 MW) High Frequency facility and
detected satellite scintillations from ground
stations in Wyoming and from aircraft for
underdense and overdense heating in
connection with the then proposed Solar
Power Satellite.
In September 1981, we used the Arecibo
heating facility at Islote and detected radio
star scintillations at 430 MHz, Plasma Line
enhancement and 50 MHz radar backscatter
from Guadeloupe over the heated volume.
In March 1984 and October 1992 we used the
EISCAT, Norway, HF transmitters with ERP of
250 MW and studied the evolution of
scintillations and irregularity structures from
Tromso, Sjorkjosen, and Grunnfjord, Norway.
(Publications: Basu et al., GRL, 1980, Basu et
al., JGR, 1983, 1987, 1997; Costa, Basu et al.,
Radio Sci., 1997)
Ionospheric Modfication Experiment at
Grunnfjord, Norway with EISCAT Heater
(Basu et al., JGR, 1997)
S. Basu and R. Livingston at an improvised
Field Site at a small fishing village!
Desert Storm and AFRL (PL) Support to the Mission
Prior to 1990, the Air Force was
focused on communication and
radar observations in the polar
and auroral regions.
During the Desert Shield phase
before the Desert Storm
Operation, we alerted the
Strategic Air Command that
Equatorial Scintillations will
impact theater communication.
We provided information on the
time of occurrence of scintillation
and the extent of their effect on
VHF, UHF, L-band and S-band
communication. This information
helped the Air Force to efficiently
prioritize the satellite
communication links during
scintillation events.
Scope of Presentation
Sunanda’s Grad Student Years
– Master’s in US – awesome discovery!
– Ph.D. in India (a son in between)
Santi’s Beacon Receiver Building Phase
– In India with his grad students
Sunanda’s Exciting NRC Post-doc Research
Sunanda and Santi Partnership Phase 1
• Sunanda’s NSF Decade – AER/CEDAR
• Sunanda and Santi Partnership Phase 2
What led to Sunanda
considering a position at NSF?
• Membership in Advisory Committee
for Atmospheric Sciences, 1988-1992
• Leading the CEDAR/High Latitude Plasma
Structure Group Workshops for many years
• Organizing the HLPS/GAPS Peaceful Valley
Workshop in Lyons, CO in June 1992
• Challenge of becoming the first woman to direct
the Aeronomy Program
• Sunanda was Aeronomy Program Dir. 1992-2002
• As luck would have it Bob Robinson and I joined
together!
Gerhard Haerendel, Director, Max
Planck Institute in Garching,
Germany, Santi and Michael
Mendillo at the ISEA-9 Meeting in
Bali Indonesia, 1995.
(I could not attend because of
major surgery)
Don Farley and me at the URSI
General Assembly in Lille, France
in 1996. As USNC/URSI Chair of
Commission G, I nominated Don for
the Appleton Prize which he won
and I wrote an article on this in the
CEDAR Post
Scientific Initiatives at NSF
AER/CEDAR Programs (1992-2002)
•
•
•
•
•
•
Comet SL 9-Jupiter-NSF AER/AST/NASA, 1996
Ionospheric Interaction - NSF/ONR/AFOSR, 1997
CEDAR-TIMED - NSF/NASA(prior to launch), 1998
Maui-MALT – NSF/AFOSR(Haleakala site), 2000
CEDAR-GEM – NSF (M/I Coupling)
Space Weather –NSF/NASA/DOC/DOD/FAA
Immediately after leaving NSF, Chaired SCOSTEP CAWSES
Program 2002-2005 – Presented the IAGA Association
and URSI General Lectures in Toulouse, France and New
Delhi, India respectively both in 2005
Germany, India and Japan had national CAWSES Programs
Around the World for CAWSES
(In 15 days in June 2004)
38,365 kilometers traveled!
SCINTILLATION NETWORK DECISION AID
(SCINDA)
• Ground-based sensor network
A REGIONAL NOWCASTING SYSTEM
– Passive UHF / L-band /GPS
scintillation receivers
– Measures scintillation intensity and
eastward drift velocity
– Automated real-time data retrieval via
internet
• Data drives equatorial
scintillation model providing
simplified visualizations for UHF
SATCOM users
• Model produces tailored
products distributed on Air
Force Weather Agency web site
Groves, Basu et al., Radio Sci. 1997
SCINDA Ground Stations
Present and anticipated thru 2008
30N
0
30S
210E
240E
270E
Existing Sites
300E
330E
0
UN IHY Sites
30E
60E
90E
120E
150E
Other/collaboration
Sensor network provides regional and global context for
ionospheric disturbances
Groves, 2008
C/NOFS:
Communication Navigation Outage Forecasting System
Santi and Ed Weber (deceased 2000) gave numerous
briefings to the Air Force Space Command on C/NOFS
Mission Concept
• 400 km x 850 km; 13° Orbital inclination
• Original launch date ~2003; Actual launch
on April 16, 2008
• C/NOFS will Specify and Forecast
Equatorial Scintillations from Satellite Insitu Measurements of
- Electron Density,
- Ion Density,
- Ion Drift
- Electric Field,
- Neutral Wind
- GPS Occultation Sensor
- Tri-Band Radio Beacon
Physics-Based Data Assimilative
C/NOFS is a joint STP/AFRL, NRL,
Model will Specify and Forecast
NASA Program
Ionospheric Scintillation
Scope of Presentation
Sunanda’s Grad Student Years
– Master’s in US – awesome discovery!
– Ph.D. in India (a son in between)
Santi’s Beacon Receiver Building Phase
– In India with his grad students
Sunanda’s Exciting NRC Post-doc Research
Sunanda and Santi Partnership Phase 1
Sunanda’s NSF Decade – AER/CEDAR
• Sunanda and Santi Partnership Phase 2
Solar Storms Disturb the Magnetosphere, Ionosphere and
Thermosphere
… and interrupt
civilian and military operations
During the main phase of large magnetic
storms an eastward electric field
penetrates from high latitudes through midlatitudes to the equator over the dayside to
the evening period.
At normally benign mid-latitudes, storm
enhanced density, associated with steep
density gradients and electron density
irregularities, is encountered in the early
afternoon period. WAAS system providing
guidance to aircraft is disabled owing to
increased GPS navigation errors. If the
penetration occurs in the evening hours,
large plasma flows introduce strong phase
scintillations and outages in GPS receivers.
NASA Simulation
At the magnetic equator, the eastward
electric field at dusk causes deep plasma
bubbles & severe scintillations,
First Study of the Ionospheric Impacts of the
Bastille Day Storm (Basu et al., GRL, 2001)
As a consequence of the PPE, the
F-region rises above DMSP. Point A denotes
location of scintillation station at Ascension
Island
Rishbeth Meeting
Sept 2010
38
The rapid time rate of change of Dst is
associated with PPE, raising F-layer,
generating bubbles & scint.
Equatorial Ionosphere Severely Impacted
During Halloween Storms in October 2003
During the Halloween Day storm of
October 30, 2003, ground stations
encountered intense TEC gradients
and ionosondes observed
spectacular height rise in the
Brazilian sector
Spectacular Height Rise of F-region
09
1000
11
30 OCTOBER 2003
13 15 17
19
21
23
31 OCTOBER 2003
01
03 05
07
09 LT
10
12
PAL
HEIGHT (km)
850
700
550
8 MHz
7 MHz
6 MHz
5 MHz
4 MHz
3 MHz
400
250
100
SJC
HEIGHT (km)
850
700
550
400
250
100
12
14
16
18
20
22
0
2
4
6
8
UNIVERSAL TIME
(Basu et al., JGR, 2007)
WAAS – A GPS-based Navigation System
•It is used for navigation and precision approach
to airports in US & parts of Canada & Mexico
•WAAS is based on ~30 GPS reference stations
•These stations are linked to form WAAS network
•Each precisely surveyed station receives GPS
signals and determines if any errors exist and
relays the data to a Master Station
•Master station computes correction information
•Master station prepares correction algorithm &
uplinks to a GEO satellite
•GEO satellite broadcasts message on GPS L1 to
receivers on aircraft flying within WAAS area
•WAAS improves basic GPS accuracy to ~7m
vertically and horizontally
Three Superstorms Considered:
Oct 29-31, 2003; Nov 20, 2003 and Nov 8, 2004
WAAS was unavailable within CONUS for more than 10 hours on each of
the above dates
WAAS Minimum Requirement for LPV is Availability > 95% of time over 75% of CONUS
(Basu et al.,RadioSc.2010)
TEC & GPS Phase Fluctuation Maps
within CONUS during the Nov 8, 2004
Magnetic Storm
GPS Outage Region
BLO
Intense GPS Phase Fluctuations (Delta TEC/MIN ) Occur Primarily in the
Auroral Region at ~ 0100 UT. GPS outage caused WAAS to be non-operational
for approximately 12 hours
(Su. Basu et al., GRL, 2005)
Impact of High Storm-time Ionospheric Velocities
on the WAAS System
GIVE Values
Green < 6 m
6<Yellow<45 m
Red > 45 m
6.13 TEC U = 1m delay
(Su. Basu et al., JGR, 2008)
Scope of Presentation
Sunanda’s Grad Student Years
– Master’s in US – awesome discovery!
– Ph.D. in India (a son in between)
Santi’s Beacon Receiver Building Phase
– In India with his grad students
Sunanda’s Exciting NRC Post-doc Research
Sunanda and Santi Partnership Phase 1
Sunanda’s NSF Decade – AER/CEDAR
Sunanda and Santi Partnership Phase 2
Lessons Learned
• Have no regrets – do the right thing
by your family at the cost of career
• Follow your passion in the choice
of your career
• Not everyone gets things handed on a platter –
working through challenges strengthens your
character. The guidance of mentors is essential
• High personal ethics is incredibly important
• Volunteerism is the backbone of our community
• Our science is so critically important to the
environment around us that we have a special role
to play in working on policy issues affecting it